The present invention generally relates to a system and methods for applying therapeutic energy to a patient for medical purposes such as reducing and/or shrinking a tissue mass. More particularly, the invention relates to an ablation catheter system that selectively contacts the tissue of a valvular annulus in order to tighten and stabilize an annular organ structure adapted for repairing an annular organ structure defect of a patient.
The circulatory system consists of a heart and blood vessels. In its path through the heart, the blood encounters four valves. The valve on the right side that separates the right atrium from the right ventricle has three cusps and is called the tricuspid valve. It closes when the ventricle contracts during a phase known as systole and it opens when the ventricle relaxes, a phase known as diastole.
The pulmonary valve separates the right ventricle from the pulmonary artery. It opens during systole, to allow the blood to be pumped toward the lungs, and it closes during diastole to keep the blood from leaking back into the heart from the pulmonary artery. The pulmonary valve has three cusps, each one resembling a crescent and it is also known as a semi-lunar valve.
The mitral valve, so named because of its resemblance to a bishop""s mitre, is in the left ventricle and it separates the left atrium from the ventricle. It opens during diastole to allow the blood stored in the atrium to pour into the ventricle, and it closes during systole to prevent blood from leaking back into the atrium. The mitral valve and the tricuspid valve differ significantly in anatomy. The annulus of the mitral valve is somewhat D-shaped whereas the annulus of the tricuspid valve is more nearly circular.
The fourth valve is the aortic valve. It separates the left ventricle from the aorta. It has three semi-lunar cusps and it closely resembles the pulmonary valve. The aortic valve opens during systole allowing a stream of blood to enter the aorta and it closes during diastole to prevent any of the blood from leaking back into the left ventricle.
In a venous circulatory system, a venous valve is to prevent the venous blood from leaking back into the upstream side so that the venous blood can return to the heart and the lungs for blood oxygenating purposes.
Clinical experience has shown that repair of a valve, either a heart valve or a venous valve, produces better long-term results than does valve replacement. Valve replacement using a tissue valve suffers long-term calcification problems. On the other hand, anticoagulation medicine, such as heparin, is required for the life of a patient when a mechanical valve is used in valve replacement. The current technology for valve repair or valve replacement requires an expensive open-heart surgery that needs a prolonged period of recovery. A less invasive catheter-based valve repair technology becomes an unmet clinical challenge.
The effects of valvular dysfunction vary. Mitral regurgitation has more severe physiological consequences to the patient than does tricuspid valve regurgitation. In patients with valvular insufficiency it is an increasingly common surgical practice to retail the natural valve, and to attempt to correct the defects. Many of the defects are associated with dilation of the valve annulus. This dilatation not only prevents competence of the valve but also results in distortion of the normal shape of the valve orifice or valve leaflets. Remodeling of the annulus is therefore central to most reconstructive procedures for the mitral valve.
As a part of the valve repair it is either necessary to diminish or constrict the involved segment of the annulus so that the leaflets may coapt correctly on closing, or to stabilize the annulus to prevent post-operative dilatation from occurring. The current open-heart approach is by implantation of a prosthetic ring, such as a Cosgrove Ring or a Carpentier Ring, in the supra annular position. The purpose of the ring is to restrict and/or support the annulus to correct and/or prevent valvular insufficiency. In tricuspid valve repair, constriction of the annulus usually takes place in the posterior leaflet segment and in a small portion of the adjacent anterior leaflet.
Various prostheses have been described for use in conjunction with mitral or tricuspid valve repair. The ring developed by Dr. Alain Carpentier (U.S. Pat. No. 3,656,185) is rigid and flat. An open ring valve prosthesis as described in U.S. Pat. No. 4,164,046 comprises a uniquely shaped open ring valve prosthesis having a special velour exterior for effecting mitral and tricuspid annuloplasty. The fully flexible annuloplasty ring could only be shortened in the posterior segment by the placement of placating sutures. John Wright et al. in U.S. Pat. No. 5,674,279 discloses a suturing ring suitable for use on heart valve prosthetic devices for securing such devices in the heart or other annular tissue. All of the above valve repair or replacement requires an open-heart operation which is costly and exposes a patient to higher risk and longer recovery than a catheter-based less invasive procedure.
Moderate heat is known to tighten and shrink the collagen tissue as illustrated in U.S. Pat. No. 5,456,662 and U. S. Pat. No. 5,546,954. It is also clinically verified that thermal energy is capable of denaturing the tissue and modulating the collagenous molecules in such a way that treated tissue becomes more resilient (xe2x80x9cThe Next Wave in Minimally Invasive Surgeryxe2x80x9d MDandDI pp. 36-44, August 1998). Therefore, it becomes imperative to treat the inner walls of an annular organ structure of a heart valve, a valve leaflet, chordae tendinae, papillary muscles, and the like by shrinking/tightening techniques. The same shrinking/tightening techniques are also applicable to stabilize injected biomaterial to repair the defect annular organ structure, wherein the injectable biomaterial is suitable for penetration and heat-initiated shrinking/tightening.
One method of reducing the size of tissues in situ has been used in the treatment of many diseases, or as an adjunct to surgical removal procedures. This method applies appropriate heat to the tissues, and causes them to shrink and tighten. It can be performed on a minimal invasive fashion, which is often less traumatic than surgical procedures and may be the only alternative method, wherein other procedures are unsafe or ineffective. Ablative treatment devices have an advantage because of the use of a therapeutic energy that is rapidly dissipated and reduced to a non-destructive level by conduction and convection, to other natural processes.
Radiofrequency (RF) therapeutic protocol has been proven to be highly effective when used by electrophysiologists for the treatment of tachycardia, atrial flutter and atrial fibrillation; by neurosurgeons for the treatment of Parkinson""s disease; by otolaryngologist for clearing airway obstruction and by neurosurgeons and anesthetists for other RF procedures such as Gasserian ganglionectomy for trigeminal neuralgia and percutaneous cervical cordotomy for intractable pains. Radiofrequency treatment, which exposes a patient to minimal side effects and risks, is generally performed after first locating the tissue sites for treatment. Radiofrequency energy, when coupled with a temperature control mechanism, can be supplied precisely to the device-to-tissue contact site to obtain the desired temperature for treating a tissue or for effecting the desired shrinking of the host collagen or injected biomaterial adapted to immobilize the biomaterial in place.
Edwards et al. in U.S. Pat. No. 6,258,087, entire contents of which are incorporated herein by reference, discloses an expandable electrode assembly comprising a support basket formed from an array of spines for forming lesions to treat dysfunction in sphincters. Electrodes carried by the spines are intended to penetrate the tissue region upon expansion of the basket. However, the assembly disclosed by Edwards et al. does not teach a tissue-contactor member comprising a narrow middle region between an enlarged distal region and an enlarged proximal region suitable for sandwiching and compressing the sphincter for tissue treatment.
Tu in U.S. Pat. No. 6,267,781 teaches an ablation device for treating valvular annulus or valvular organ structure of a patient, comprising a flexible elongate tubular shaft having a deployable spiral wire electrode at its distal end adapted to contact/penetrate the tissue to be treated and to apply high frequency energy to the tissue for therapeutic purposes. Tu et al. in U.S. Pat. No. 6,283,962 discloses a medical ablation device system for treating valvular annulus wherein an elongate tubular element comprises an electrode disposed at its distal section that is extendible from an opening at one side of the tubular element, the energy generator, and means for generating rotational sweeping force at the distal section of the tubular element to effect the heat treatment and the rotational sweeping massage therapy for target tissues. Both patents, entire contents of which are incorporated herein by reference, teach only the local tissue shrinkage, not for treating simultaneously a substantial portion of the valvular annulus.
Therefore, there is a clinical need to have a less invasive catheter-based approach for repairing an annular organ structure of a heart valve, a valve leaflet, chordae tendinae, papillary muscles, and the tissue defect by using high frequency energy for reducing and/or shrinking a tissue mass, with optionally an injected biomaterial along with the host tissue mass for tightening and stabilizing the dilated tissue adjacent a valvular annulus.
In general, it is an object of the present invention to provide a catheter system and methods for repairing an annular organ structure of a heart valve, an annular organ structure of a venous valve, a valve leaflet, chordae tendinae, papillary muscles, a sphincter, and the like.
It is another object of the present invention to provide a catheter system and methods by using high frequency current for tissue treatment or repairing and causing the tissue to shrink or tighten.
It is still another object to provide a catheter-based less invasive system that contacts the tissue of an annulus in order to tighten and stabilize a substantial portion of the dysfunctional annular organ structure simultaneously or sequentially.
It is a preferred object to provide a method for repairing a valvular annulus defect comprising injecting a heat shapeable biomaterial formulated for in vivo administration by injection via a delivery system at a site of the valvular annulus defect; and applying heat sufficient to shape the biomaterial and immobilize the biomaterial at about the annulus defect.
It is another preferred object of the present invention to provide a flexible tissue-contactor member located at the distal tip section of a catheter shaft for compressively sandwiching and contacting an inner wall of an annular organ structure, wherein the tissue-contactor member includes an expandable structure having a narrow middle region and enlarged end regions that is generally configured to snugly fit and sandwich the inner wall of an annular organ structure for optimal therapy that is characterized by exerting compression onto the inner wall.
It is another object of the invention to provide a method for repairing a tissue defect comprising: injecting a heat shapeable biomaterial formulated for in vivo administration by injection via a percutaneous delivery system at a site of the tissue defect; and applying heat to the biomaterial and a portion of the tissue defect adapted for shaping the biomaterial, the heat being below a temperature sufficient for effecting crosslinking of the biomaterial and the portion of the tissue defect.
It is still another object of the present invention to provide a catheter system and methods for providing high frequency current energy to the tissue needed for treatment at or adjacent an annular organ structure.
In one embodiment, the method for operating a catheter system for repairing a valvular annulus or a valveless annulus comprising compressively sandwiching the annulus by a tissue-contactor member and delivering high frequency energy to the annulus, wherein the tissue-contactor member is configured to have a narrow middle region between an enlarged distal region and an enlarged proximal region adapted for compressively sandwiching the annulus at about the middle region for subsequent tissue treatment.
The catheter system of the present invention has several significant advantages over known catheters or ablation techniques for repairing an annular organ structure of a heart valve, a valve leaflet, chordae tendinae, papillary muscles, venous valve, and the like. In particular, the ablation catheter of this invention by using high frequency current energy for reducing and/or shrinking a tissue mass may tighten and stabilize the dilated tissue at or adjacent a valvular annulus.